The present invention relates to a device for connection of a nozzle of a pre-mixing chamber of a gas turbine, to a housing of the pre-mixing chamber.
It is known that gas turbines comprise a compressor, to which air is supplied from the external environment in order to pressurise the compressor. The compressed air passes into a series of pre-mixing chambers, which end in a nozzle, in each of which an injector supplies fuel which is mixed with the air in order to form an air/fuel mixture to be burnt. When the mixture passes through the nozzle, it enters the combustion chamber, where it burns, and produces gases with a high level of enthalpy, which are expanded in a turbine. The turbine transforms the enthalpy of the gases into mechanical energy which is available to a user.
The present invention relates in particular to nozzles which admit the mixture which is formed in the pre-mixer inside the combustion chamber, and to the device for connection of the nozzles to a housing of a pre-mixing chamber. These nozzles consist of generally converging elements, and are commonly known as shrouds.
In order to make apparent the technical problems which are covered by the present invention, hereinafter a brief description is provided of a single pre-mixing unit 10, with reference to FIG. 1.
The pre-mixing unit 10 comprises a pre-mixing chamber 11, which is defined by a housing 12 integral with a column-type support 13. The column-type support 13 ends in a plate 14, in which there are provided through holes 15 for attachment to a motor body, not shown, and a pair of through holes 16 which constitute the ends of pipes 17, 18 for supply of the fuel.
One pipe 17 opens into an annular chamber 19, from which, via through holes 20, a portion of the fuel is supplied to an air agitator device 21, generally indicated as a swirler. In the swirler 21 and the pre-mixing chamber 11, there is produced the mixture consisting of air with a high level of turbulence obtained from the compressor, and a portion of fuel supplied via the swirler 21.
The swirler 21 generally consists of two separate concentric blade elements: an outer element 21a is provided with blades which are oriented in one direction, whereas an inner element 21b, which is inserted on a shaped ogival element 22, is provided with blades which are oriented in the opposite direction.
The different orientation of the blades of the two elements 21a and 21b of the swirler 21 makes it possible to obtain downstream from the swirler 21 itself, in the pre-mixing chamber 11, a high level of turbulence which creates ideal conditions for obtaining a highly dispersed air-fuel mixture, and thus satisfactory combustion. It will be appreciated that, as shown in FIG. 1, the through holes 20 admit the fuel into the outer element 21a of the swirler 21.
The column-type support 13 has another pipe 18 which supplies to a series of pipes, which, in conventional embodiments (not shown in FIG. 1) open inside the nozzle 23. More particularly, these pipes open in the vicinity of a mouth of the nozzle 23, which faces the combustion chamber of the turbine.
The pre-mixing chambers, and in particular the nozzles in which these chambers end, and by means of which they are connected to the combustion chamber, are parts of the turbines which are subject to thermal stress.
Since the flame in the combustion chamber is kept anchored in the vicinity of the nozzle, it transmits high thermal loads to all the elements of the pre-mixing unit, and in particular to the nozzle which is the element closest to it.
The foregoing makes apparent the fact that since the nozzle is the element which is under the greatest mechanical and thermal stress, it is also the element which is destined to become worn and damaged most.
For this reason, the nozzles generally consist of elements which are separate from the housing of the pre-mixing chamber, and are connected to the latter in a removable or detachable manner, such that they can be maintained, and when necessary replaced.
In the conventional embodiments, the nozzle is connected directly to the housing of the pre-mixing chamber. This means that removal of the connection and separation of the nozzle from the housing of the pre-mixing chamber are somewhat lengthy and difficult. In addition, in order to be able to produce sealed connections between the nozzle and the housing, accurate work is necessary, which is substantially lengthy, difficult and costly.
The object of the present invention is to eliminate the above-described technical disadvantages, by providing a device for connection of a nozzle of a pre-mixing chamber of a gas turbine, to a housing of the pre-mixing chamber, which makes it possible to carry out rapid, simple connections of the nozzle to the housing of the pre-mixing chamber.
Another object of the invention is to provide a device for connection of a nozzle to a pre-mixing chamber of a gas turbine, to a housing of the pre-mixing chamber, which makes it possible to disconnect the nozzle from the housing of the pre-mixing chamber in a substantially fast, simple manner.
A further object of the invention is to provide a device for connection of a nozzle of a pre-mixing chamber of a gas turbine, to a housing of the pre-mixing chamber, which makes it possible to maintain and optionally replace the nozzle of the mixing unit in a substantially fast, simple manner.
A further object of the invention is to -provide a device for connection of a nozzle of a pre-mixing chamber of a gas turbine, to a housing of the pre-mixing chamber, which is substantially simple, safe and reliable.
This and other objects of the present invention are achieved by providing a device for connection of a nozzle of a pre-mixing chamber of a gas turbine, to a housing of the pre-mixing chamber, characterised in that it comprises at least one flange which clasps and retains the said nozzle, the said flange being connected in a detachable manner to the said housing of the said pre-mixing chamber, so as to render the said nozzle integral with the said housing of the said pre-mixing chamber.
According to a preferred embodiment, the flange is produced by means of a bush element, in which the nozzle is inserted, with one of the ends connected in a non-detachable manner to the nozzle, and the other end connected in a detachable manner to the pre-mixing chamber.
According to another preferred embodiment, the nozzle has an annular cavity, which is surrounded by the bush element. Between the annular cavity of the nozzle and the bush element, there is provided a distribution chamber, which can be supplied with fuel by a first pipe, and from which the fuel is discharged, and is admitted into the combustion chamber downstream from the nozzle, via second pipes.
Further characteristics of the device for connection according to the invention are also defined in the claims.
Advantageously, the device for connection according to the present invention is not only economical in terms of its production, but also because it makes it possible to carry out interventions on the nozzle or on the housing of the pre-mixing chamber in a manner which is substantially more economical than according to the known art.